Motor-driven compressor

ABSTRACT

A motor-driven compressor includes an electric motor including a rotor, a housing, a compression unit, a drive circuit, and a controller. The controller includes a deceleration controller that performs a deceleration control, which decelerates the rotor, during a first period in response to the rotor being rotating in a direction opposite to the forward direction, and a continuation controller that performs a continuation control, which continues the rotation of the rotor, during a second period that is longer than the first period after the deceleration control is performed. A fluctuation difference of a rotational frequency of the rotor during the continuation control is less than a deceleration rotational frequency difference.

BACKGROUND OF THE INVENTION

The present invention relates to a motor-driven compressor.

Japanese Laid-Open Patent Publication No. 2003-120555 discloses anexample of a motor-driven compressor that includes a compression unit,which includes a fixed scroll and a movable scroll capable of orbitingthe fixed scroll, and an electric motor, which includes a rotor andcauses the movable scroll to orbit. The motor-driven compressor includesa compression chamber that is defined by the fixed scroll and themovable scroll and draws in an intake fluid. The orbiting of the movablescroll compresses the intake fluid in the compression chamber anddischarges the compressed fluid.

Japanese Laid-Open Patent Publication No. 2003-120555 also describes amotor-driven compressor that includes an injection port, which draws anintermediate pressure fluid having higher pressure than the intake fluidinto the compression chamber, and an air conditioner including themotor-driven compressor. The air conditioner includes, for example, aninjection pipe connected to the injection port and a gas-liquidseparator connected to the injection pipe. The intermediate pressurefluid flows out of the gas-liquid separator and into the compressionchamber through the injection pipe and the injection port. Thisincreases the flow rate of the fluid flowing into the compressionchamber.

When the motor-driven compressor, which is configured to draw theintermediate pressure fluid into the compression chamber as describedabove, is deactivated, the residual intermediate pressure liquid in theinjection pipe may flow into the compression chamber through theinjection port. This may result in a reverse rotation action in whichthe movable scroll orbits in a direction opposite to the forwarddirection and reverses the rotation of the rotor. In this situation,noise and vibration tend to increase when the rotational frequency(rotation speed) of the rotor is high.

To promptly stop the rotor, the electric motor may undergo, for example,a forcible deactivation control that forcibly stops the reverse rotationof the rotor. In this case, the intermediate pressure fluid may continueto remain in the injection pipe. The intermediate pressure fluid maycause a reverse rotation recurrence action in which after the rotationof the rotor is stopped, the rotor reversely rotates again. The reverserotation recurrence action may interfere with, for example, theactivation of the motor-driven compressor.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a motor-drivencompressor that limits the occurrence of reverse rotation recurrenceactions while limiting noise and vibration.

To achieve the above object, a motor-driven compressor includes anelectric motor including a rotor, a housing including a suction portthat draws in a fluid, a compression unit driven by the electric motor,a drive circuit that drives the electric motor, and a controller thatcontrols the drive circuit to control rotation of the rotor. Thecompression unit compresses an intake fluid, which is the fluid drawn infrom the suction port, and discharges a compressed fluid, which is thecompressed intake fluid. The compression unit includes a fixed scrollfixed to the housing, a movable scroll engaged with the fixed scroll andconfigured to orbit the fixed scroll, and a compression chamber definedby the fixed scroll and the movable scroll. When the rotor rotates in apredetermined forward direction, the movable scroll orbits in theforward direction, and the compression unit thereby compresses theintake fluid drawn into the compression chamber. The motor-drivencompressor further includes an injection port that draws an intermediatepressure fluid into the compression chamber. The intermediate pressurefluid has a pressure that is higher than the intake fluid and lower thanthe compressed fluid. The controller includes a deceleration controllerthat performs a deceleration control, which decelerates the rotor,during a first period in response to the rotor being rotating in adirection opposite to the forward direction, and a continuationcontroller that performs a continuation control, which continues therotation of the rotor, during a second period that is longer than thefirst period after the deceleration control is performed. A fluctuationdifference of a rotational frequency of the rotor during thecontinuation control is less than a deceleration rotational frequencydifference, which is a difference between a rotational frequency of therotor when the deceleration control is started and a rotationalfrequency of the rotor when the deceleration control is terminated.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic cross-sectional view of a motor-driven compressor;

FIG. 2 is a cross-sectional view of a compression unit of themotor-driven compressor shown in FIG. 1;

FIG. 3 is a schematic diagram of a vehicle air conditioner;

FIG. 4 is a circuit diagram showing the electrical configuration of aninverter;

FIG. 5 is a time chart showing lower arm switching elements in aone-phase pattern in which (a) shows activation and deactivation of au-phase lower arm switching element, (b) shows activation anddeactivation of a v-phase lower arm switching element, and (c) showsactivation and deactivation of a w-phase lower arm switching element;

FIG. 6 is a schematic graph showing each phase current when a rotorrotates in a forward direction;

FIG. 7 is a schematic graph showing each phase current when the rotorrotates in a direction opposite to the forward direction;

FIG. 8 is a flowchart of a reverse rotation control process;

FIG. 9 is a time chart showing the lower arm switching elements in atwo-phase pattern in which (a) shows activation and deactivation of theu-phase lower arm switching element, (b) shows activation anddeactivation of the v-phase lower arm switching element, and (c) showsactivation and deactivation of the w-phase lower arm switching element;and

FIG. 10 is a graph showing changes in the rotational frequency of therotor subsequent to deactivation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of a motor-driven compressor will now be described.

As shown in FIG. 1, a motor-driven compressor 10 includes a housing 11provided with a suction port 11 a, which draws in a fluid, and an outlet11 b, which discharges the fluid. The housing 11 is tubular as a whole.More specifically, the housing 11 includes a first part 12 and a secondpart 13, each of which is tubular and has a closed end and an open end.The first part 12 and the second part 13 are coupled to each other withthe open ends opposed to each other. The suction port 11 a is located ina side wall 12 a of the first part 12, more specifically, a portion ofthe side wall 12 a of the first part 12 located proximate to a closedend 12 b of the first part 12. The outlet 11 b is located in a closedend 13 a of the second part 13.

The motor-driven compressor 10 includes a rotation shaft 14, acompression unit 15, which compresses the fluid drawn from the suctionport 11 a, namely, the intake fluid, and discharges the fluid out of theoutlet 11 b, and an electric motor 16, which drives the compression unit15. The rotation shaft 14, the compression unit 15, and the electricmotor 16 are accommodated in the housing 11. The electric motor 16 islocated in the housing 11 at a side corresponding to the suction port 11a. The compression unit 15 is located in the housing 11 at a sidecorresponding to the outlet 11 b.

The rotation shaft 14 is rotationally accommodated in the housing 11.More specifically, the housing 11 accommodates a shaft support member21, which rotationally supports the rotation shaft 14. The shaft supportmember 21 is fixed to the housing 11, for example, at a position betweenthe compression unit 15 and the electric motor 16. The shaft supportmember 21 is provided with an insertion hole 23 around which a firstbearing 22 is arranged. The rotation shaft 14 may be inserted throughthe insertion hole 23. The shaft support member 21 is opposed to theclosed end 12 b of the first part 12. A tubular boss 24 projects fromthe closed end 12 b. A second bearing 25 is located at an inner side ofthe boss 24. The rotation shaft 14 is rotationally supported by thefirst bearing 22 and the second bearing 25.

The compression unit 15 includes a fixed scroll 31, which is fixed tothe housing 11, and a movable scroll 32, which is capable of orbitingthe fixed scroll 31.

The fixed scroll 31 includes a disk-shaped fixed base plate 31 a, whichis coaxial with the rotation shaft 14, and a fixed spiral wall 31 b,which projects from the fixed base plate 31 a. In the same manner, themovable scroll 32 includes a disk-shaped movable base plate 32 a, whichis opposed to the fixed base plate 31 a, and a movable spiral wall 32 b,which projects from the movable base plate 32 a toward the fixed baseplate 31 a.

As shown in FIGS. 1 and 2, the fixed scroll 31 and the movable scroll 32are engaged with each other. More specifically, the fixed spiral wall 31b and the movable spiral wall 32 b are engaged with each other, thefixed spiral wall 31 b includes a distal surface that is in contact withthe movable base plate 32 a, and the movable spiral wall 32 b includes adistal surface that is in contact with the fixed base plate 31 a. Thefixed scroll 31 and the movable scroll 32 define a compression chamber33. As shown in FIG. 1, the shaft support member 21 includes an intakepassage 34 that draws the intake fluid into the compression chamber 33.

The movable scroll 32 is configured to orbit in accordance with therotation of the rotation shaft 14. More specifically, the rotation shaft14 partially projects through the insertion hole 23 of the shaft supportmember 21 toward the compression unit 15. The rotation shaft 14 includesan end surface that is opposed to the compression unit 15. An eccentricshaft 35 is located on a portion of the end surface that is eccentric toan axis L of the rotation shaft 14. A bushing 36 is located on theeccentric shaft 35. The bushing 36 is coupled to the movable scroll 32(more specifically, movable base plate 32 a) by the bearing 37.

The motor-driven compressor 10 includes a rotation restriction portion38 that restricts rotation of the movable scroll 32 while allowing forthe orbiting of the movable scroll 32. The motor-driven compressor 10includes a plurality of rotation restriction portions 38.

In this structure, when the rotation shaft 14 rotates in a predeterminedforward direction, the movable scroll 32 orbits in the forwarddirection. More specifically, the movable scroll 32 orbits in theforward direction about the axis of the fixed scroll 31 (i.e., axis L ofrotation shaft 14). This reduces the volume of the compression chamber33 and compresses the intake fluid, which has been drawn into thecompression chamber 33 through the intake passage 34. The compressedintake fluid, namely, the compressed fluid, is discharged from adischarge port 41 of the fixed base plate 31 a and then the outlet 11 b.The forward direction may be also referred to as the direction in whichthe fluid is compressed in a normal manner.

As shown in FIG. 1, a discharge valve 42 is located on the fixed baseplate 31 a to cover the discharge port 41. The compressed fluid, whichhas been compressed in the compression chamber 33, pushes the dischargevalve 42 aside and is discharged from the discharge port 41.

As shown in FIGS. 1 and 2, the fixed base plate 31 a includes injectionports 43 in addition to the discharge port 41. The fixed base plate 31 aincludes, for example, a plurality of injection ports 43, morespecifically, two injection ports 43. The injection ports 43 arearranged in the fixed base plate 31 a at a radially outer side of thedischarge port 41. The injection ports 43 are connected to an injectionpipe 119. The connected subject of the injection pipe 119 will bedescribed later.

The electric motor 16 rotates the rotation shaft 14 to drive theorbiting of the movable scroll 32. As shown in FIG. 1, the electricmotor 16 includes a rotor 51, which rotates integrally with the rotationshaft 14, and a stator 52, which surrounds the rotor 51. The rotor 51 iscoupled to the rotation shaft 14. The rotor 51 includes a permanentmagnet (not shown). The stator 52 is fixed to an inner surface of thehousing 11 (more specifically, first part 12). The stator 52 includes astator core 53, which is radially opposed to the tubular rotor 51, and acoil 54, which is wound around the stator core 53.

The motor-driven compressor 10 includes an inverter 55, which functionsas a drive circuit that drives the electric motor 16. The inverter 55 isaccommodated in the housing 11, more specifically, a tubular covermember 56 coupled to the closed end 12 b of the first part 12. Theinverter 55 is electrically connected to the coil 54.

In the present embodiment, the motor-driven compressor 10 is installedin a vehicle and used with a vehicle air conditioner 100. Thus, in thepresent embodiment, the fluid compressed by the motor-driven compressor10 is a refrigerant. The vehicle air conditioner 100 will now bedescribed in detail.

As shown in FIG. 3, the vehicle air conditioner 100 includes a pipeswitch valve 101, a first heat exchanger 102, a second heat exchanger103, a first expansion valve 104, a second expansion valve 105, and agas-liquid separator 106.

The pipe switch valve 101 includes ports 101 a to 101 d. The pipe switchvalve 101 switches to a first state or a second state. In the firststate, the first port 101 a is in communication with the second port 101b, and the third port 101 c is in communication with the fourth port 101d. In the second state, the first port 101 a is in communication withthe third port 101 c, and the second port 101 b is in communication withthe fourth port 101 d.

The vehicle air conditioner 100 includes a first pipe 111, whichconnects the first port 101 a and the outlet 11 b of the motor-drivencompressor 10, a second pipe 112, which connects the second port 101 band the first heat exchanger 102, and a third pipe 113, which connectsthe first heat exchanger 102 and the first expansion valve 104. Thevehicle air conditioner 100 also includes a fourth pipe 114, whichconnects the first expansion valve 104 and the gas-liquid separator 106,a fifth pipe 115, which connects the gas-liquid separator 106 and thesecond expansion valve 105, a sixth pipe 116, which connects the secondexpansion valve 105 and the second heat exchanger 103, and a seventhpipe 117, which connects the second heat exchanger 103 and the thirdport 101 c. Additionally, the vehicle air conditioner 100 includes aneighth pipe 118, which connects the fourth port 101 d and the suctionport 11 a of the motor-driven compressor 10.

In this structure, the injection pipe 119, which is connected to theinjection ports 43, is connected to the gas-liquid separator 106.Additionally, a check valve 120 is located in the injection pipe 119.

The vehicle air conditioner 100 of the present embodiment is capable ofperforming a cooling operation and a heating operation. Morespecifically, the vehicle air conditioner 100 includes anair-conditioning ECU 121 that controls the entire vehicle airconditioner 100 including the pipe switch valve 101. Theair-conditioning ECU 121 switches the pipe switch valve 101 to the firststate, for example, during the cooling operation. In this case, therefrigerant is discharged from the outlet 11 b and sent to the firstheat exchanger 102. The refrigerant condenses when exchanging heat withexternal air in the first heat exchanger 102. The condensed refrigerantis reduced in pressure by the first expansion valve 104 and then sent tothe gas-liquid separator 106. The refrigerant is separated into liquidand gas by the gas-liquid separator 106. The liquid refrigerant isreduced in pressure by the second expansion valve 105 and then sent tothe second heat exchanger 103. The liquid refrigerant evaporates whenexchanging heat with the air of the passenger compartment at the secondheat exchanger 103. This cools the air in the passenger compartment. Therefrigerant evaporated in the second heat exchanger 103 flows toward thesuction port 11 a of the motor-driven compressor 10. During the coolingoperation, the check valve 120 is closed.

The air-conditioning ECU 121 switches the pipe switch valve 101 to thesecond state, for example, during the heating operation. In this case,the refrigerant is discharged from the outlet 11 b and sent to thesecond heat exchanger 103. The refrigerant condenses when exchangingheat with the air in the passenger compartment at the second heatexchanger 103. This heats the air in the passenger compartment. Therefrigerant condensed in the second heat exchanger 103 is reduced inpressure by the second expansion valve 105 and then sent to thegas-liquid separator 106. The refrigerant is separated into fluid andgas in the gas-liquid separator 106. The separated liquid refrigerant isreduced in pressure in the first expansion valve 104 and then sent tothe first heat exchanger 102. The refrigerant evaporates when exchangingheat with the external air at the first heat exchanger 102. Theevaporated refrigerant flows to the suction port 11 a.

The check valve 120 is open during the heating operation. Thus, thegaseous refrigerant, which has been separated by the gas-liquidseparator 106, flows to the compression chamber 33 through the injectionpipe 119 and the injection ports 43. This increases the flow rate of therefrigerant flowing into the compression chamber 33.

The gaseous fluid separated in the gas-liquid separator 106, which isthe refrigerant drawn into the compression chamber 33 through theinjection ports 43, has a pressure that is higher than the refrigerantdrawn in from the suction port 11 a and lower than the refrigerantdischarged from the outlet 11 b. For the sake of brevity, in thedescription hereafter, the refrigerant that is drawn in from the suctionport 11 a is referred to as the intake refrigerant. The refrigerant thatis discharged from the outlet 11 b is referred to as the compressedrefrigerant. The refrigerant that is drawn into the compression chamber33 from the injection ports 43 is referred to as the intermediatepressure refrigerant. The intake refrigerant corresponds to an “intakefluid.” The compressed refrigerant corresponds to a “compressed fluid.”

In the vehicle air conditioner 100 having the above structure, after themotor-driven compressor 10 is deactivated, the intermediate pressurefluid remains in the injection pipe 119. The motor-driven compressor 10of the present embodiment is configured to appropriately discharge theintermediate pressure fluid. The configuration will now be describedtogether with the electrical configuration of the coil 54 of theelectric motor 16 and the inverter 55.

The electrical configuration between the coil 54 and the inverter 55will now be described. As shown in FIG. 4, the coil 54 has a three-phasestructure including, for example, a u-phase coil 54 u, a v-phase coil 54v, and a w-phase coil 54 w. Thus, the electric motor 16 is a three-phasemotor. The phase coils 54 u, 54 v, 54 w are, for example, Y-connected.

The inverter 55 includes a u-phase upper arm switching element Qu1 and au-phase lower arm switching element Qu2, which correspond to the u-phasecoil 54 u. In the same manner, the inverter 55 includes a v-phase upperarm switching element Qv1 and a v-phase lower arm switching element Qv2,which correspond to the v-phase coil 54 v, and a w-phase upper armswitching element Qw1 and a w-phase lower arm switching element Qw2,which correspond to the w-phase coil 54 w. Thus, the inverter 55 is aso-called three-phase inverter.

The switching elements Qu1, Qu2, Qv1, Qv2, Qw1, Qw2 are each formed, forexample, by an IGBT. Instead, a power MOSFET or the like may be used.

The inverter 55 includes two power lines EL1, EL2 that are connected toa DC power supply E installed in the vehicle. The inverter 55 furtherincludes a u-phase wire ELu connected to the power lines EL1, EL2. Theu-phase switching elements Qu1, Qu2 are arranged in the u-phase wire ELuand connected in series to each other by the u-phase wire ELu. Theportion of the u-phase wire ELu that connects the u-phase switchingelements Qu1, Qu2 is connected to the u-phase coil 54 u. The DC powersupply E is a power storage device such as a battery or an electricdouble-layer capacitor.

In the same manner, the inverter 55 includes a v-phase wire ELvconnected to the power lines EL1, EL2. The v-phase switching elementsQv1, Qv2 are arranged in the v-phase wire ELv. The portion of thev-phase wire ELv that connects the v-phase switching elements Qv1, Qv2is connected to the v-phase coil 54 v. The inverter 55 includes aw-phase wire ELw connected to the power lines EL1, EL2. The w-phaseswitching elements Qw1, Qw2 are arranged in the w-phase wire ELw. Theportion of the w-phase wire ELw that connects the w-phase switchingelements Qw1, Qw2 is connected to the w-phase coil 54 w.

The inverter 55 includes a smoothing capacitor C1 connected in parallelto the DC power supply E. The inverter 55 also includes flyback diodesDu1 to Dw2 that are connected in parallel to the switching elements Qu1to Qw2, respectively. The flyback diodes Du1 to Dw2 may be parasiticdiodes of the switching elements Qu1 to Qw2. Alternatively, the flybackdiodes Du1 to Dw2 may be separate from the switching elements Qu1 toQw2.

The motor-driven compressor 10 includes a control device 60, whichfunctions as a controller that controls the inverter 55 (morespecifically, switching operations of switching elements Qu1 to Qw2) tocontrol the rotation of the rotor 51. The control device 60 is connectedto the gates of the switching elements Qu1 to Qw2. The control device 60may be formed by one or more dedicated hardware circuits and/or one ormore processors (control circuitry) that operate in accordance with acomputer program (software). A processor includes a CPU and a memorysuch as a RAM or a ROM. The memory stores program codes or instructionsimplemented so that the processor executes, for example, the processshown in FIG. 8. The memory, that is, a computer readable medium,includes any usable medium that is accessible using a versatile ordedicated computer.

The control device 60 performs PWM control on the inverter 55. Morespecifically, the control device 60 uses a carrier signal (transportwave signal) and an instruction voltage signal (comparison signal) togenerate a control signal. The control device 60 uses the generatedcontrol signal to cyclically apply a voltage having a predeterminedpulse width δT to each of the switching elements Qu1 to Qw2. Thiscyclically activates and deactivates each of the switching elements Qu1to Qw2. Consequently, DC power of the DC power supply E is convertedinto AC power. The AC power is supplied to the electric motor 16 todrive, or generate rotation, with the electric motor 16. The controldevice 60 is configured to be capable of changing the pulse width δT,that is, the activation/deactivation duty ratio for each of theswitching elements Qu1 to Qw2.

When activating the motor-driven compressor 10, the control device 60recognizes the rotation position (rotation angle) where the rotor 51that is still is located and controls the switching elements Qu1 to Qw2to rotate the rotor 51 based on the recognition result. Morespecifically, the rotor 51 needs to be still when activating themotor-driven compressor 10. Any specific structure may be used torecognize the rotation position of the rotor 51.

The control device 60 is configured to be capable of recognizing phasecurrents Iu, Iv, Iw that flow to the phase coils 54 u, 54 v, 54 w as thecurrent flowing to the electric motor 16. More specifically, as shown inFIG. 4, the inverter 55 includes current sensors 61 to 63, whichfunction as current detectors that respectively detect the currentflowing through the phase wires ELu to ELw. The current sensors 61 to 63are located, for example, between the second power line EL2 and thelower arm switching elements Qu2 to Qw2 of the respective phase wiresELu to ELw. The current sensors 61 to 63 transmit the detection resultsto the control device 60. The control device 60 is capable ofrecognizing u-phase current Iu, which is the current flowing to theu-phase coil 54 u, v-phase current Iv, which is the current flowing tothe v-phase coil 54 v, and w-phase current Iw, which is the currentflowing to the w-phase coil 54 w, based on the detection results of thecurrent sensors 61 to 63.

The current sensors 61 to 63 may have any specific configuration. Forexample, when the configuration includes a shunt resistor, the phasecurrents Iu to Iw may be estimated from the voltage applied to the shuntresistor.

The control device 60 and the air-conditioning ECU 121 are electricallyconnected to each other and capable of exchanging information with eachother. The control device 60 activates or deactivates the motor-drivencompressor 10 in response to a request, an abnormality determinationresult, or the like received from the air-conditioning ECU 121. Thedeactivation of the motor-driven compressor 10 refers to a condition inwhich the supply of AC power to the electric motor 16 is stopped, morespecifically, when all of the switching elements Qu1 to Qw2 aredeactivated.

After a predetermined waiting period elapses from the deactivation ofthe motor-driven compressor 10, the control device 60 of the presentembodiment executes a recognition process that recognizes the rotationdirection of the rotor 51 and the rotational frequency R, or therotation speed, of the rotor 51 based on the detection results of thecurrent sensors 61 to 63. The control device 60 that executes therecognition process corresponds to a “recognition unit.”

More specifically, the control device 60 maintains the upper armswitching elements Qu1, Qv1, Qw1, which are located at a side notcorresponding to the current sensors 61 to 63, in the deactivationstate, while the control device 60 cyclically activates and deactivatesthe lower arm switching elements Qu2, Qv2, Qw2, which are located at aside corresponding to the current sensors 61 to 63, using apredetermined switching pattern. In the present embodiment, the lowerarm switching elements Qu2, Qv2, Qw2 are subject to the switching (i.e.,activation/deactivation) and correspond to “subject arm switchingelements of the three phases.”

The control device 60 controls, for example, the lower arm switchingelements Qu2, Qv2, Qw2 using a switching pattern (hereafter, referred toas the one-phase pattern) in which the lower arm switching elements Qu2,Qv2, Qw2 of the three phases are sequentially activated one phase at atime in a predetermined order and that includes a mode in which thelower arm switching element of one phase is activated, while the lowerarm switching elements of the remaining two phases are deactivated. Inthe present embodiment, as shown in (a) to (c) of FIG. 5, the one-phasepattern switches the lower arm switching element that is activated inorder from the u-phase lower arm switching element Qu2 to the v-phaselower arm switching element Qv2 and then the w-phase lower arm switchingelement Qw2.

A mode having the combination of Qu2 being activated while Qu1, Qv1,Qw1, Qv2, Qw2 being deactivated is referred to as the first mode. A modehaving the combination of Qv2 being activated while Qu1, Qv1, Qw1, Qu2,Qw2 being deactivated is referred to as the second mode. In this case,the control device 60 switches from the first mode to the second mode bycyclically activating and deactivating the lower arm switching elementsQu2, Qv2, Qw2. In other words, the switching mode used in thedeceleration control (one-phase pattern) includes the first mode and thesecond mode, which have different combinations of the activated anddeactivated switching elements Qu1 to Qw2.

The one-phase pattern is a switching pattern that is set so that amongthe lower arm switching elements Qu2, Qv2, Qw2 of the three phases, thelower arm switching elements of multiple phases (two phases or threephases) are not simultaneously activated.

The one-phase pattern is not limited to the switching pattern in whichthe lower arm switching element of any one of the three phases isconstantly activated as shown in (a) to (c) of FIG. 5 and may include aninterval period during which the lower arm switching elements Qu2, Qv2,Qw2 are all deactivated. The one-phase pattern may be a switchingpattern in which, for example, the lower arm switching elements aresequentially activated one phase at a time in a predetermined orderbetween the above interval periods and the lower arm switching elementof one phase is activated, while the lower arm switching elements of theremaining two phases are deactivated.

In the present embodiment, the lower arm switching elements Qu2, Qv2,Qw2 rise to the activation state at different timings that are separatedfrom each other by a predetermined period δa. More specifically, theperiod from when the lower arm switching element Qu2 rises to when thelower arm switching element Qv2 rises, the period from when the lowerarm switching element Qv2 rises to when the lower arm switching elementQw2 rises, and the period from when the lower arm switching element Qw2rises to when the lower arm switching element Qu2 rises are the samepredetermined period δa. In this configuration, the one-phase pattern isa switching pattern in which the pulse width δT is set to be less thanor equal to the predetermined period δa. When the pulse width δT is lessthan the predetermined period δa, the one-phase pattern is a switchingpattern in which the lower arm switching elements are sequentiallyactivated one phase at a time in the predetermined order between theinterval periods (three-phase deactivation periods). When the pulsewidth δT is equal to the predetermined period δa, the one-phase patternis a switching pattern in which the lower arm switching elements aresequentially activated one phase at a time in the predetermined orderwithout the interval period.

The relationship between the rotation direction and the rotationalfrequency R of the rotor 51 and the phase currents Iu, Iv, Iw will nowbe described with reference to FIGS. 6 and 7.

FIG. 6 is a schematic graph showing the phase currents Iu, Iv, Iwdetected when the rotor 51 is rotating in the forward direction. FIG. 7is a schematic graph showing the phase currents Iu, Iv, Iw detected whenthe rotor 51 is rotating in the reverse direction. To facilitateillustration, in FIGS. 6 and 7, a cycle of a minimal unit wave (singletriangle wave) of each of the phase currents Iu, Iv, Iw is elongatedfrom the actual cycle.

FIGS. 6 and 7 show the current waveforms of the phase currents Iu, Iv,Iw when the lower arm switching elements Qu2, Qv2, Qw2 are constantlyactivated and deactivated. Thus, the actual switching of the lower armswitching elements Qu2, Qv2, Qw2 in the one-phase pattern obtainsone-third of the number of triangle waves that are formed by the phasecurrents Iu, Iv, Iw shown in FIGS. 6 and 7.

As shown in FIGS. 6 and 7, the phase currents Iu, Iv, Iw (morespecifically, envelopes of phase currents Iu, Iv, Iw) have differentphases. Thus, a phase current having a positive value sequentiallyshifts as time elapses. A phase current has a positive value when thephase coil corresponding to the phase current having the positive valuegenerates smaller counter-electromotive force than the other phasecoils.

The shifting order of the phase current having a positive value differsbetween when the rotor 51 is rotating in the forward direction and whenthe rotor 51 is rotating in the reverse direction. More specifically, asshown in FIG. 6, when the rotor 51 is rotating in the forward direction,the phase current having a positive value shifts in order from theu-phase current Iu to the v-phase current Iv and then the w-phasecurrent Iw. However, as shown in FIG. 6, when the rotor 51 is rotatingin the reverse direction, the phase current having a positive valueshifts in order from the w-phase current Iw to the v-phase current Ivand then the u-phase current Iu.

A positive current period Ta during which the phase current has apositive value corresponds to one-third of one cycle of the electricalangle of the rotor 51.

The control device 60 recognizes the rotation direction and therotational frequency R of the rotor 51 based on the above properties andthe current waveforms obtained from the detection results of the currentsensors 61 to 63 when the lower arm switching elements Qu2, Qv2, Qw2 areswitched in the one-phase pattern.

More specifically, when the lower arm switching elements Qu2, Qv2, Qw2are switched in the one-phase pattern, current waveforms of the phasecurrents Iu, Iv, Iw are obtained in correspondence with the presentrotation direction and the present rotational frequency R. The controldevice 60 recognizes the shifting order of the phase current having apositive value from the current waveforms. The control device 60determines whether the rotation direction of the rotor 51 is forward orreverse based on the recognition results.

The control device 60 recognizes the positive current period Ta from thecurrent waveforms obtained by switching in the one-phase pattern. Thecontrol device 60 derives the rotational frequency R of the rotor 51based on the recognized positive current period Ta.

The above properties do not change even when the switching pattern ofthe lower arm switching elements Qu2, Qv2, Qw2 changes. Morespecifically, the properties include an aspect such that the shiftingorder of the phase current having a positive value differs in accordancewith the rotation direction and an aspect such that the positive currentperiod Ta corresponds to one-third of one cycle of the rotor 51. Thus,even when the lower arm switching elements Qu2, Qv2, Qw2 are switched ina two-phase pattern, the control device 60 recognizes the rotationdirection and the rotational frequency R of the rotor 51 based on theabove properties and the current waveforms obtained from the currentsensors 61 to 63. The detail of the two-phase pattern will be describedlater.

In response to being recognizing that the rotor 51 is rotating in thereverse direction through the recognition process, the control device 60executes a reverse rotation control process that controls the rotationalfrequency of the rotor 51 that is rotating in the reverse direction. Thereverse rotation control process will now be described.

As shown in FIG. 8, in step S101, the control device 60 executes adeceleration control that decreases the rotational frequency R to atarget rotational frequency Rt. The control device 60 that executes theprocess of step S101 corresponds to a “deceleration controller.”

The target rotational frequency Rt is set to be less than or equal to apredetermined rotational frequency tolerance Ra. More specifically, whenthe rotor 51 is reversely rotating, the motor-driven compressor 10generates noise, vibration, or the like. The noise and the vibrationtend to increase as the rotational frequency R increases. In thisaspect, the rotational frequency tolerance Ra is the maximum value atwhich the noise and the vibration are allowed.

The deceleration control of the present embodiment will now be describedin detail. In the deceleration control, the control device 60decelerates the rotor 51 by activating at least one of the switchingelements Qu1 to Qw2. In the present embodiment, in the decelerationcontrol, the control device 60 cyclically activates and deactivates thelower arm switching elements Qu2, Qv2, Qw2 at a predetermined switchingpattern to sequentially switch the lower arm switching element that isactivated. More specifically, in the deceleration control, the controldevice 60 uses a switching control mode that switches(activates/deactivates) the lower arm switching elements Qu2, Qv2, Qw2to sequentially switch the lower arm switching element that isactivated. The sequential switching of the lower arm switching elementthat is activated indicates that the combination of the activated anddeactivated switching elements Qu1 to Qw2 (more specifically, the lowerarm switching elements Qu2, Qv2, Qw2) is sequentially changed.

In this case, the lower arm switching elements Qu2, Qv2, Qw2 are set tohave the same switching frequency.

In this configuration, when the positive phase current corresponds tothe lower arm switching element that is activated, heat is generated inthe phase coil corresponding to the lower arm switching element that isactivated. This converts kinetic energy of the rotor 51 into thermalenergy and decelerates the rotor 51. In the description hereafter, theeffect that decelerates the rotor 51 by converting the kinetic energy ofthe rotor 51 into thermal energy is referred to as the brake effect.

The phase current and the phase coil that correspond to the lower armswitching element that is activated refer to the u-phase current Iu andthe u-phase coil 54 u when the u-phase lower arm switching element Qu2is activated. In the same manner, the v-phase current Iv and the v-phasecoil 54 v are referred to when the v-phase lower arm switching elementQv2 is activated. The w-phase current Iw and the w-phase coil 54 w arereferred to when the w-phase lower arm switching element Qw2 isactivated.

In this configuration, as the phase currents Iu, Iv, Iw increase, heattends to be generated. This increases the brake effect. Morespecifically, as the phase currents Iu, Iv, Iw increase, a largerdeceleration force tends to be applied to the rotor 51.

The counter-electromotive force generated in the phase coils 54 u, 54 v,54 w increases as the rotational frequency R increases. Additionally,the phase currents Iu, Iv, Iw increase more easily as thecounter-electromotive force increases. Thus, the phase currents Iu, Iv,Iw are dependent on the rotational frequency R.

In this regard, the control device 60 starts the deceleration control bycyclically activating and deactivating the lower arm switching elementsQu2, Qv2, Qw2 using a predetermined initial deceleration duty ratio anda predetermined initial deceleration switching pattern. In the presentembodiment, the initial switching pattern is the one-phase pattern. Theinitial deceleration duty ratio is set in accordance with apredetermined tolerance value and the counter-electromotive forcegenerated when the rotational frequency R is the expected maximum valueso that the phase currents Iu, Iv, Iw flowing because of the switchingin the one-phase pattern do not exceed the tolerance value when therotational frequency R is the maximum value that is expected under asituation in which the intermediate pressure refrigerant causes reverserotation. More specifically, the initial deceleration duty ratio and theinitial switching pattern are set so that the phase currents Iu, Iv, Iwdo not exceed the tolerance value regardless of the rotational frequencyR of the rotor 51. The tolerance value is, for example, the ratedcurrent value of the switching elements Qu1 to Qw2 or a value that islower than the rated current value by a predetermined margin.

Then, the control device 60 variably controls at least one of theswitching pattern and the activation/deactivation duty ratio of thelower arm switching elements Qu2, Qv2, Qw2 so that the phase currentsIu, Iv, Iw increase within a range that does not exceed the tolerancevalue based on the detection results of the phase currents Iu, Iv, Iw.The control device 60, for example, gradually increases the duty ratiofrom the initial deceleration duty ratio so that the phase currents Iu,Iv, Iw do not exceed the tolerance value.

As described above, in the switching pattern of the present embodiment,the lower arm switching elements Qu2, Qv2, Qw2 rise to the activationstate at different timings that are separated from each other by apredetermined period δa. More specifically, the period from when thelower arm switching element Qu2 rises to when the lower arm switchingelement Qv2 rises, the period from when the lower arm switching elementQv2 rises to when the lower arm switching element Qw2 rises, and theperiod from when the lower arm switching element Qw2 rises to when thelower arm switching element Qu2 rises are the same predetermined periodδa. When the duty ratio increases and the pulse width δT of each of thelower arm switching elements Qu2, Qv2, Qw2 becomes greater than thepredetermined period δa, the switching pattern is switched from theone-phase pattern to the two-phase pattern.

As shown in (a) to (c) of FIG. 9, the two-phase pattern is a switchingpattern in which the lower arm switching elements Qu2, Qv2, Qw2 of thethree phases are sequentially activated two phases at a time in apredetermined order and that includes a mode in which the lower armswitching elements of two phases are activated, while the lower armswitching element of the remaining phase is deactivated. In thetwo-phase pattern, the lower arm switching elements that are activatedare switched, for example, in the order of the u-phase lower armswitching element Qu2 and the v-phase lower arm switching element Qv2,the v-phase lower arm switching element Qv2 and the w-phase lower armswitching element Qw2, the w-phase lower arm switching element Qw2 andthe u-phase lower arm switching element Qu2, and so on. In the two-phasepattern of the present embodiment, the upper arm switching elements Qu1,Qv1, Qw1 all remain in the deactivation state.

For example, a mode having the combination of Qu2, Qv2 being activatedwhile Qu1, Qv1, Qw1, Qw2 being deactivated is referred to as the firstmode. A mode having the combination of Qv2, Qw2 being activated whileQu1, Qv1, Qw1, Qu2 being deactivated is referred to as the second mode.In this case, the control device 60 switches from the first mode to thesecond mode by cyclically activating and deactivating the lower armswitching elements Qu2, Qv2, Qw2. In other words, the switching modeused in the deceleration control (two-phase pattern) includes the firstmode and the second mode, which have different combinations of theactivated and deactivated switching elements Qu1 to Qw2.

The two-phase pattern is not limited to the switching pattern in whichthe lower arm switching elements of any two of the three phases areconstantly activated as shown in (a) to (c) of FIG. 9 and may include aone-phase activation period in which the lower arm switching element ofone phase is activated while the lower arm switching elements of the twophases are deactivated. The two-phase pattern may be a switching patternin which switching occurs in the order of, for example, Qu2 is activatedwhile Qv2, Qw2 are deactivated; Qu2, Qv2 are activated while Qw2 isdeactivated; Qv2 is activated while Qu2, Qw2 are deactivated; Qv2, Qw2are activated while Qu2 is deactivated; Qw2 is activated while Qu2, Qv2are deactivated; Qu2, Qw2 are activated while Qv2 is deactivated; and soon. Thus, the two-phase pattern may be a switching pattern in which thelower arm switching elements are sequentially activated two phases at atime in a predetermined order between one-phase activation periods(two-phase deactivation periods).

The two-phase pattern may include a three-phase activation period duringwhich the lower arm switching elements Qu2, Qv2, Qw2 are all activated.The two-phase pattern may be a switching pattern in which switchingoccurs in the order of, for example, Qu2, Qv2 are activated while Qw2 isdeactivated; Qu2, Qv2, Qw2 are activated; Qv2, Qw2 are activated whileQu2 is deactivated; Qu2, Qv2, Qw2 are activated; Qu2, Qw2 are activatedwhile Qv2 is deactivated; Qu2, Qv2, Qw2 are activated; Qu2, Qv2 areactivated while Qw2 is deactivated; and so on. Thus, the two-phasepattern may be a switching pattern in which the lower arm switchingelements are sequentially activated two phases at a time in apredetermined order between the three-phase activation periods.

When the pulse width δT of each of the lower arm switching elements Qu2,Qv2, Qw2 is less than twice the predetermined period δa, the two-phasepattern is a switching pattern in which the lower arm switching elementsare sequentially activated two phases at a time in the predeterminedorder between the one-phase activation periods. When the pulse width δTof each of the lower arm switching elements Qu2, Qv2, Qw2 is greaterthan twice the predetermined period δa, the two-phase pattern is aswitching pattern in which the lower arm switching elements aresequentially activated two phases at a time in the predetermined orderbetween the three-phase activation periods. When the pulse width δT ofeach of the lower arm switching elements Qu2, Qv2, Qw2 is equal to twicethe predetermined period δa, the two-phase pattern is a switchingpattern in which the lower arm switching elements are sequentiallyactivated two phases at a time in the predetermined order without theone-phase activation period and the three-phase activation period. Thebrake effect tends to increase as the duty ratio increases.

When the lower arm switching elements Qu2, Qv2, Qw2 are configured to beswitched in the two-phase pattern, a mode is used in which the lower armswitching elements of two phases are simultaneously activated. Thus, thelower arm switching element corresponding to the phase current having apositive value is activated at a switching frequency of two out of threetimes under the mode. Therefore, the two-phase pattern increases thephase currents Iu, Iv, Iw more easily than the one-phase pattern.

After the switching pattern is switched from the one-phase pattern tothe two-phase pattern, the control device 60 further gradually increasesthe duty ratio in a range such that the phase currents Iu, Iv, Iw do notexceed the tolerance value.

The phase currents Iu, Iv, Iw are dependent on the rotational frequencyR. Thus, during deceleration in which the rotational frequency R isgradually decreased, the actual phase currents Iu, Iv, Iw do not alwaysincrease even when the switching pattern and the duty ratio are variablycontrolled to easily increase the phase currents in a gradual manner.More specifically, the variable control of the switching pattern and theduty ratio that function to increase the phase currents Iu, Iv, Iw in agradual manner does not necessarily increase the actual phase currentsIu, Iv, Iw and only needs to limit decreases in the phase currents Iu,Iv, Iw in accordance with the deceleration.

The control device 60 recognizes the present rotational frequency R ofthe rotor 51 from waveforms of the phase currents Iu, Iv, Iw obtained bythe deceleration control. The control device 60 continues thedeceleration control until the rotational frequency R becomes the targetrotational frequency Rt and terminates the deceleration control when therotational frequency R becomes the target rotational frequency Rt. Thetime when execution of the process of step S101 is started correspondsto the time when the deceleration control is started. The time when therotational frequency R becomes the target rotational frequency Rtcorresponds to the time when the deceleration control is terminated. Thecontrol device 60 stores a first period T1, which is the executionperiod of the deceleration control. The first period T1 varies inaccordance with the state during the deactivation.

As shown in FIG. 8, when the rotational frequency R decreases to thetarget rotational frequency Rt, the control device 60 proceeds to stepS102 and executes a continuation control that continues the reverserotation of the rotor 51. The control device 60 that executes theprocess of step S102 corresponds to a “continuation controller.”

In the continuation control, the control device 60 controls the inverter55 so that the rotational frequency R is maintained at the targetrotational frequency Rt. More specifically, the control device 60 startsthe continuation control by cyclically activating and deactivating thelower arm switching elements Qu2, Qv2, Qw2 using a predetermined initialcontinuation switching pattern and a predetermined initial continuationduty ratio. In the present embodiment, the initial continuationswitching pattern and the initial continuation duty ratio are aswitching pattern and a duty ratio that are set when the decelerationcontrol is terminated.

The intermediate pressure refrigerant is discharged during the reverserotation of the rotor 51. The discharging of the intermediate pressurerefrigerant decreases the pressure of the intermediate pressurerefrigerant in the injection pipe 119. This reduces kinetic energy thatreversely rotates the rotor 51. Thus, when the switching controlcontinues in the same mode, the rotational frequency R graduallydecreases due to the reduction in the kinetic energy corresponding tothe reverse rotation of the rotor 51.

In this regard, in the present embodiment, the control device 60variably controls at least one (in present embodiment, both) of theswitching pattern and the duty ratio so that the phase currents Iu, Iv,Iw gradually decrease. More specifically, the control device 60gradually decreases the duty ratio so that the rotational frequency R ismaintained at the target rotational frequency Rt. Additionally, when theswitching pattern is the two-phase pattern and the duty ratio becomes alower limit value corresponding to the two-phase pattern, the controldevice 60 switches the switching pattern to the one-phase pattern andfurther gradually decreases the duty ratio.

In this configuration, thermal energy consumed by the electric motor 16decreases in correspondence with the decrease in the kinetic energyresulting from the discharge of the intermediate pressure refrigerant.This tends to maintain the rotational frequency R at the targetrotational frequency Rt.

The control device 60 recognizes the present rotational frequency R fromwaveforms of the phase currents Iu, Iv, Iw obtained by the continuationcontrol and performs feedback control on the switching pattern and theduty ratio so that the obtained rotational frequency R becomes close tothe target rotational frequency Rt. More specifically, during thecontinuation control, the control device 60 controls the phase currentsIu, Iv, Iw in accordance with changes in the pressure of theintermediate pressure refrigerant in the injection pipe 119 so that therotational frequency R becomes close to the target rotational frequencyRt.

The control device 60 executes the continuation control during a secondperiod T2 that is longer than the first period T1, which is theexecution period of the deceleration control. More specifically, duringthe continuation control, the control device 60 regularly determineswhether or not a predetermined continuation control terminationcondition is satisfied. The continuation control termination conditionincludes, for example, both condition (A) in which the execution periodof the continuation control (i.e., second period T2) is longer than thefirst period T1 and condition (B) in which the phase currents Iu, Iv, Iware less than or equal to a predetermined termination trigger currentvalue.

The termination trigger current value is set in correspondence with astate in which the intermediate pressure refrigerant has beensufficiently discharged from the injection pipe 119, in other words, astate in which after being stopped, the rotor 51 will not be moved bythe intermediate pressure refrigerant. More specifically, the controldevice 60 includes map data in which the switching control modes (morespecifically, switching pattern and duty ratio) are associated with thetermination trigger current values. Each termination trigger currentvalue corresponds to the phase currents Iu, Iv, Iw obtained when thepressure of the residual intermediate pressure refrigerant in theinjection pipe 119 is a predetermined tolerance pressure value duringexecution of the switching control associated with the terminationtrigger current value.

The control device 60 recognizes the termination trigger current valuecorresponding to the present switching control mode by referring to themap data and determines whether or not the phase currents Iu, Iv, Iwthat flow because of the switching control are less than or equal to thetermination trigger current value. When the phase currents Iu, Iv, Iware less than or equal to the termination trigger current value, thecontrol device 60 determines that condition (B) is satisfied.

The control device 60 continues the execution of the continuationcontrol until the continuation control termination condition issatisfied.

When the continuation control termination condition is satisfied, thecontrol device 60 proceeds to step S103 and executes a deactivationcontrol that stops the rotor 51. More specifically, the control device60 maintains all of the lower arm switching elements Qu2, Qv2, Qw2 inthe activation state. That is, the control device 60 short-circuits allof the phase coils 54 u, 54 v, 54 w. The deactivation control may bereferred to as the deceleration control in which the lower arm switchingelements Qu2, Qv2, Qw2 of the three phases are all set to the activationstate and the duty ratio is set to 100%.

The operation of the present embodiment will now be described withreference to FIG. 10. FIG. 10 is a schematic graph showing changes inthe rotational frequency R subsequent to the deactivation. In FIG. 10,“+” denotes the forward rotation, and “−” denotes the reverse rotation.

As shown in FIG. 10, at time t1, when the motor-driven compressor 10 isdeactivated, the rotational frequency R of the rotor 51 graduallydecreases. At time t2, the rotation direction of the rotor 51 isswitched from the forward direction to the reverse direction.Subsequently, the rotational frequency R becomes greater than the targetrotational frequency Rt and the rotational frequency tolerance Ra.

At time t3, the recognition process is executed. When the reverserotation of the rotor 51 is recognized, the deceleration control isstarted. Consequently, the kinetic energy is converted into thermalenergy, and the rotor 51 starts to decelerate. In this case, asdescribed above, the brake effect gradually increases. Thus, thedeceleration rate of the rotational frequency R gradually increases.

At time t4, when the rotational frequency R becomes equal to the targetrotational frequency Rt, the deceleration control is switched to thecontinuation control. In this case, the first period T1 is from time t3to time t4. The difference in the rotational frequency R between timet3, which is the start time of the deceleration control, and time t4,which is the termination time of the deceleration control, is referredto as a deceleration rotational frequency difference δR1 (decelerationrotation speed difference).

During the continuation control, the rotational frequency R ismaintained at the target rotational frequency Rt. In this case, theactual rotational frequency R does not completely conform to the targetrotational frequency Rt and slightly fluctuates. However, a continuationrotational frequency difference δR2 (continuation rotation speeddifference), which is the difference between the minimum value and themaximum value of the rotational frequency R during the continuationcontrol, is sufficiently smaller than the deceleration rotationalfrequency difference δR1. The continuation rotational frequencydifference δR2 corresponds to the fluctuation difference of therotational frequency R of the rotor 51 during the continuation control.

At time t5, when the continuation control termination condition issatisfied, the switching control is switched from the continuationcontrol to the termination control. At time t6, the reverse rotation ofthe rotor 51 stops. In this case, the second period T2 is from time t4to time t5.

The present embodiment has the advantages described below.

(1) The motor-driven compressor 10 includes the electric motor 16including the rotor 51, the housing 11, which is provided with thesuction port 11 a that draws in the refrigerant functioning as a fluid,and the compression unit 15, which compresses the intake refrigerantthat is drawn in from the suction port 11 a and discharges thecompressed refrigerant. The compression unit 15 includes the fixedscroll 31, which is fixed to the housing 11, the movable scroll 32,which is engaged with the fixed scroll 31 and capable of orbiting thefixed scroll 31, and the compression chamber 33 defined by the fixedscroll 31 and the movable scroll 32. The compression unit 15 isconfigured to compress the intake refrigerant, which is drawn into thecompression chamber 33, when the movable scroll 32 orbits in the forwarddirection as the rotor 51 rotates in the forward direction.

In this configuration, the motor-driven compressor 10 includes theinjection ports 43, which draw the intermediate pressure refrigeranthaving a pressure that is higher than the intake refrigerant and lowerthan the compressed refrigerant into the compression chamber 33, theinverter 55, which drives the electric motor 16, and the control device60, which controls the inverter 55. The control device 60 executes thedeceleration control, which decelerates the rotor 51, during the firstperiod T1 in response to the rotor 51 being rotating in a directionreverse to the forward direction. After terminating the decelerationcontrol, the control device 60 executes the continuation control, whichcontinues the reverse rotation of the rotor 51, during the second periodT2, which is longer than the first period T1. The continuationrotational frequency difference δR2 (continuation rotation speeddifference), which is the difference between the maximum value and theminimum value of the rotational frequency R (rotation speed) of therotor 51 obtained during the continuation control, is smaller than thedeceleration rotational frequency difference δR1 (deceleration rotationspeed difference), which is the difference in the rotational frequency Rbetween the start time of the deceleration control and the terminationtime of the deceleration control.

In this configuration, when the rotor 51 is reversely rotating, therotor 51 is decelerated during the first period T1. Then, the reverserotation of the rotor 51 continues at a relatively low rotationalfrequency R during the second period T2, which is longer than the firstperiod T1. Thus, the intermediate pressure refrigerant is dischargedwhile limiting noise and vibration.

More specifically, noise and vibration tend to increase as therotational frequency R increases. Thus, if the high rotational frequencyR continues for a long time, noise and vibration may be annoying.However, if the rotor 51 is forcibly and quickly stopped, theintermediate pressure refrigerant continues to remain in the injectionpipe 119. This may cause the reverse rotation recurrence action in whichafter the rotation of the rotor 51 is stopped, the rotor 51 reverselyrotates again. The reverse rotation recurrence action displaces therotation position of the rotor 51 and may interfere with the activationof the motor-driven compressor 10 in which the switching elements Qu1 toQw2 are controlled based on the rotation position of the rotor 51.

In this regard, in the present embodiment, the deceleration control isfirst performed. Then, when the rotational frequency R is decreased, thecontinuation control is performed. In the continuation control, thefluctuation of the rotational frequency R is small compared to thedeceleration control. This allows the continuation control to easilymaintain the reverse rotation of the rotor 51 at a relatively lowrotational frequency R. Thus, the noise and the vibration are limitedduring the continuation control. Additionally, the continuation controlis performed during the second period T2, which is longer than the firstperiod T1. This appropriately discharges the intermediate pressurerefrigerant. Additionally, the first period T1, which is the executionperiod of the deceleration control corresponding to a relatively highrotational frequency R, is shorter than the second period T2. Thus, thenoise and the vibration may not be annoying. Therefore, occurrences ofthe reverse rotation recurrence action are limited while limiting thenoise and the vibration. This limits the interference with theactivation of the motor-driven compressor 10 that is caused by theintermediate pressure refrigerant.

(2) In the deceleration control, the control device 60 decelerates therotor 51 until the rotational frequency R of the rotor 51 becomes thetarget rotational frequency Rt, which is set to be less than or equal tothe predetermined rotational frequency tolerance Ra. In the continuationcontrol, the control device 60 continues the rotation of the rotor 51during the second period T2 while maintaining the rotational frequency Rat the rotational frequency tolerance Ra or lower. In thisconfiguration, during the continuation control, the rotational frequencyR is less than or equal to the rotational frequency tolerance Ra. Thislimits the noise and the vibration in a further favorable manner.

(3) In the continuation control, the control device 60 controls theinverter 55 so that the rotational frequency R is maintained at thetarget rotational frequency Rt. In this configuration, the rotationalfrequency R is maintained at a high level compared to a configurationthat gradually decreases the rotational frequency R from the targetrotational frequency Rt. This facilitates the discharging of theintermediate pressure refrigerant and promptly discharges theintermediate pressure refrigerant. Consequently, the second period T2may be shortened. This shortens the period until the rotor 51 isstopped.

(4) The inverter 55 includes the upper arm switching elements Qu1, Qv1,Qw1 and the lower arm switching elements Qu2, Qv2, Qw2, in which thoseof the same phase are connected to each other. The control device 60controls the switching elements Qu1 to Qw2. In the deceleration control,the control device 60 sequentially switches the lower arm switchingelement that is activated by cyclically activating and deactivating thelower arm switching elements Qu2, Qv2, Qw2 while maintaining the upperarm switching elements Qu1, Qv1, Qw1 in the deactivation state.

In this configuration, when the phase current flows in correspondencewith the lower arm switching element that is activated, the kineticenergy of the rotor 51 is converted into thermal energy. Thisdecelerates the rotor 51.

The lower arm switching elements Qu2, Qv2, Qw2 may be maintained in theactivation state without being cyclically activated and deactivated.However, if the lower arm switching elements Qu2, Qv2, Qw2 aremaintained in the activation state, the phase currents Iu, Iv, Iw wouldexcessively increase and exceed the tolerance value. In this regard, inthe present embodiment, the lower arm switching elements Qu2, Qv2, Qw2are configured to be cyclically activated and deactivated. This limitsexcessive increases in the phase currents Iu, Iv, Iw.

Additionally, in the present embodiment, the lower arm switching elementthat is activated is sequentially switched. Thus, the phase currents Iu,Iv, Iw have the same level. This reduces the phase current of each phasefor obtaining the desired brake effect. Thus, excessive increases in thephase currents Iu, Iv, Iw are limited when decelerating the rotor 51.Accordingly, the rotational frequency of the rotor 51 is promptlydecreased while limiting interference in the operation of the inverter55 that would be caused by excessive increases in the current flowing tothe electric motor 16. This limits noise and vibration.

Additionally, since the lower arm switching element that is activated issequentially switched, differences in the heat generation amount arereduced among the three lower arm switching elements Qu2, Qv2, Qw2. Thislimits situations in which only a certain lower arm switching elementgenerates excessive heat among the three lower arm switching elementsQu2, Qv2, Qw2. Consequently, the rotor 51 is decelerated while limitingthe local heat generation of the certain lower arm switching element.

(5) In particular, the brake effect is obtained when the lower armswitching element corresponding to the phase current having a positivevalue is activated. The lower arm switching element to which the phasecurrent having a positive value may flow is sequentially switched in apredetermined order. Thus, if the lower arm switching element of onlyone designated phase is configured to be cyclically activated anddeactivated, the deceleration is performed only during a period in whichthe phase current corresponding to the designated phase has a positivevalue. In this case, the rotor 51 is intermittently decelerated. Thismay result in, for example, a failure to obtain the sufficient brakeeffect or unstable reverse rotation of the rotor 51.

In this regard, in the present embodiment, the lower arm switchingelement that is activated is sequentially switched. Thus, the lower armswitching element corresponding to the phase current having a positivevalue is activated at a predetermined frequency (in present embodiment,at least one of three times). This allows for continuous decelerationand limits the above unfavorable situations.

Further, for example, the positive current period Ta of each of thephase currents Iu, Iv, Iw may be recognized in advance to control cyclicactivation and deactivation of only the lower arm switching element thatcorresponds to the positive current period Ta. However, to perform thiscontrol, the rotation position of the rotor 51 needs to be recognized.Further, the rotation position needs to be synchronized with theswitching of the lower arm switching elements Qu2, Qv2, Qw2. This mayresult in the need for a separate rotational angle sensor such as aresolver or the need to perform complicated control and thereby causethe configuration to be complicated.

In this regard, in the present embodiment, the lower arm switchingelement that is activated is sequentially switched as described above.Thus, the rotor 51 decelerates without the need to recognize therotation position of the rotor 51 or synchronize the rotation positionwith the switching of the lower arm switching elements Qu2, Qv2, Qw2.This simplifies the configuration.

(6) The control device 60 starts the deceleration control by cyclicallyactivating and deactivating the lower arm switching elements Qu2, Qv2,Qw2 using the predetermined initial deceleration switching pattern andthe predetermined initial deceleration duty ratio. Then, the controldevice 60 variably controls at least one of the switching pattern andthe duty ratio of the lower arm switching elements Qu2, Qv2, Qw2 so thatthe phase currents Iu, Iv, Iw increase in a range that does not exceedthe tolerance value. In this configuration, the rotational frequency Rof the rotor 51 is decreased in a relatively prompt manner whilelimiting excessive increases in the phase currents Iu, Iv, Iw whenstarting the deceleration control.

More specifically, the phase currents Iu, Iv, Iw increases more easilyas the rotational frequency R of the rotor 51 increases. Thus, if theswitching pattern and the duty ratio that easily increase the phasecurrents Iu, Iv, Iw are set from the beginning of the decelerationcontrol, which is when the rotational frequency R is high, the phasecurrents Iu, Iv, Iw would have a tendency to excessively increase.However, if the deceleration control is continued using the switchingpattern and the duty ratio that easily decrease the phase currents Iu,Iv, Iw, decreases in the rotational frequency R of the rotor 51 would beimpeded.

In this regard, in the present embodiment, the deceleration controlstarts using the initial deceleration switching pattern and the initialdeceleration duty ratio, and then the lower arm switching elements Qu2,Qv2, Qw2 are controlled to increase in a range such that the phasecurrents Iu, Iv, Iw do not exceed the tolerance value. This increasesthe brake effect while limiting a situation in which the phase currentsIu, Iv, Iw excessively increase when starting the deceleration control.This allows the first period T1 to be shortened.

(7) The control device 60 starts the continuation control by cyclicallyactivating and deactivating the lower arm switching elements Qu2, Qv2,Qw2 using the initial continuation switching pattern and the initialcontinuation duty ratio. Then, the control device 60 variably controlsat least one of the switching pattern and the duty ratio of the lowerarm switching elements Qu2, Qv2, Qw2 so that the phase currents Iu, Iv,Iw gradually decrease. In this configuration, after the continuationcontrol is started, thermal energy consumed by the electric motor 16gradually decreases. Thus, during the continuation control, therotational frequency R is maintained at a certain level even when thekinetic energy gradually decreases due to decreases in the pressure whenthe intermediate pressure refrigerant is discharged from the injectionports 43. This avoids a situation in which the continuation rotationalfrequency difference δR2 exceeds the deceleration rotational frequencydifference δR1.

(8) After terminating the continuation control, the control device 60executes the deactivation control, which stops the rotation of the rotor51. In this configuration, the rotation of the rotor 51 is promptlystopped compared to a configuration in which the rotor 51 spontaneouslydecelerates after terminating the continuation control. This shortensthe period from when the deceleration control is started until when thereverse rotation of the rotor 51 is stopped.

(9) The control device 60 recognizes the rotation direction and therotational frequency R of the rotor 51 based on the phase currents Iu,Iv, IW that flow under the deceleration control and the continuationcontrol. In this configuration, the rotation direction and therotational frequency R of the rotor 51 are recognized without using adedicated sensor or the like. This may achieve a sensor-lessconfiguration. Further, the deceleration control and the continuationcontrol may be effectively utilized by recognizing the rotationdirection and the rotational frequency R of the rotor 51 based on thephase currents Iu, Iv, Iw flowing as a result of the decelerationcontrol and the continuation control. In other words, energizationcontrol dedicated to the recognition of the rotation direction and therotational frequency R of the rotor 51 does not need to be performed.This may simplify the control.

The above embodiment may be modified as follows.

The continuation control is not limited to a control that maintains therotational frequency R at the target rotational frequency Rt. Thecontinuation control may be, for example, a control that graduallydecreases the rotational frequency R in a range such that thecontinuation rotational frequency difference δR2 is less than thedeceleration rotational frequency difference δR1.

In the continuation control, the control device 60 may control the lowerarm switching elements Qu2, Qv2, Qw2 so that the rotational frequency Rincreases in a range that is less than or equal to the rotationalfrequency tolerance Ra. Alternatively, the control device 60 mayalternately repeat acceleration and deceleration. The continuationcontrol only needs to be executed for a longer time than the firstperiod T1 when the continuation rotational frequency difference δR2 isless than the deceleration rotational frequency difference δR1. Therotational frequency R may be changed in any specific mode during thecontinuation control. The difference in the rotational frequency Rbetween when the deceleration control is started and when thedeceleration control is terminated may be used as the continuationrotational frequency difference δR2.

The deceleration control and the continuation control are not limited tothose of the embodiment and may have any specific switching controlmode. The control device 60 may be configured, for example, tocyclically activate and deactivate the lower arm switching element ofonly a predetermined fixed phase and maintain the lower arm switchingelement of the remaining phases in the deactivation state.Alternatively, the control device 60 may be configured to cyclicallyactivate and deactivate the lower arm switching elements Qu2, Qv2, Qw2of the three phases by synchronizing the rising timing and the fallingtiming.

In the deceleration control, the control device 60 only needs to use theswitching pattern and the duty ratio that increase the phase currentsIu, Iv, Iw more easily as the rotational frequency R decreases. Theswitching pattern and the duty ratio may be changed in any specificmode.

In the deceleration control, the control device 60 may be configured notto change the switching pattern and the duty ratio from the initialdeceleration switching pattern and the initial deceleration duty ratio.In the same manner, in the continuation control, the control device 60may be configured not to change the switching pattern and the duty ratiofrom the initial continuation switching pattern and the initialcontinuation duty ratio.

The initial continuation switching pattern and the initial continuationduty ratio are not limited to the switching pattern and the duty ratiothat are obtained when the deceleration control is terminated and may beany switching pattern and any duty ratio as long as the rotationalfrequency R does not excessively fluctuate.

The target rotation frequency Rt that triggers the termination of thedeceleration control may differ from the target rotation frequency Rtthat is maintained in the continuation control. The control device 60may, for example, execute the deceleration control until the rotationalfrequency R becomes a first target rotational frequency and thencontinue the reverse rotation of the rotor 51 so that the rotationalfrequency R becomes close to a second target rotational frequency ratherthan the first target rotational frequency. In this case, the secondtarget rotational frequency is preferably less than or equal to therotational frequency tolerance Ra. The first target rotational frequencymay be less than or equal to the rotational frequency tolerance Ra orslightly greater than the rotational frequency tolerance Ra.

The deactivation control may be omitted. In this case, the rotor 51spontaneously decelerates and stops.

The termination trigger condition for the deceleration control is notlimited to a state in which the rotational frequency R becomes thetarget rotational frequency Rt. The termination trigger condition forthe deceleration control may be, for example, a state in which apredetermined first period T1 ends from the start time of thedeceleration control.

Condition (B) may be omitted from the continuation control terminationcondition. In this case, the second period T2 is preferably set so thatthe intermediate pressure refrigerant is sufficiently dischargedregardless of the state during the deactivation.

When condition (B) is omitted, the second period T2 may be set incorrespondence with the first period T1. The second period T2 may beset, for example, to be longer as the first period T1 shortens.Consequently, when the discharge amount of the intermediate pressurerefrigerant is small due to the short first period T1 during thedeceleration control, the discharge amount of the intermediate pressurerefrigerant may be increased during the continuation control. Thisappropriately discharges the intermediate pressure refrigerant.

In the embodiment, the subject arm switching elements of the threephases, which are subject to the switching, are the lower arm switchingelements Qu2, Qv2, Qw2. Instead, for example, the upper arm switchingelements Qu1, Qv1, Qw1 may be used. More specifically, the controldevice 60 may cyclically activate and deactivate the upper arm switchingelements Qu1, Qv1, Qw1 so that the upper arm switching element that isactivated is sequentially switched. In this case, the lower armswitching elements Qu2, Qv2, Qw2 preferably maintain, for example, thedeactivation state. The current sensors 61 to 63 are preferably arrangedon the phase wires ELu to ELw between the upper arm switching elementsQu1, Qv1, Qw1 and the first power line EL1.

Thus, in the deceleration control, the control device 60 may use aswitching control mode that switches the upper arm switching elementsQu1, Qv1, Qw1 to sequentially switch the upper arm switching elementthat is activated.

The control device 60 may switch (i.e., cyclically activate anddeactivate) both the upper arm switching elements Qu1, Qv1, Qw1 and thelower arm switching elements Qu2, Qv2, Qw2. More specifically, thesubject arm switching elements of the three phases, which are subject tothe switching, may be both the upper arm switching elements Qu1, Qv1,Qw1 of the three phases and the lower arm switching elements Qu2, Qv2,Qw2 of the three phases. In this case, the control device 60 preferablycontrols the switching elements so that the upper arm switching elementand the lower arm switching element of the same phase are notsimultaneously activated. More specifically, the control device 60 mayuse a switching control mode that sequentially switches the upper armswitching element that is activated and also sequentially switches thelower arm switching element that is activated so that the upper armswitching element and the lower arm switching element of the same phaseare not simultaneously activated.

More specifically, in the deceleration control, the control device 60only needs to decelerate the rotor 51 by activating at least one of theupper arm switching elements Qu1, Qv1, Qw1 of the three phases and thelower arm switching elements Qu2, Qv2, Qw2 of the three phases. In thiscase, the switching control mode used by the control device 60 in thedeceleration control only needs to include the first mode, in which oneor more of the switching elements Qu1 to Qw2 are activated while theremaining switching elements are deactivated, and the second mode, whichdiffers from the first mode in the combination of the switching elementthat is activated and the switching element that is deactivated. Thislimits situations in which only a certain switching element locallygenerates heat. Thus, the rotor 51 is appropriately decelerated.

The second mode only needs to differ from the first mode in thecombination of the activation and deactivation states of the switchingelements Qu1 to Qw2. Thus, in the second mode, some of the switchingelements of the phases that are activated may be the same as the firstmode. In the two-phase pattern, for example, a mode in which Qu2, Qv2are activated while Qu1, Qv1, Qw1, Qw2 are deactivated is referred to asthe first mode. A mode in which Qv2, Qw2 are activated while Qu1, Qv1,Qw1, Qu2 are deactivated is referred to as the second mode. In thiscase, the v-phase lower arm switching element Qv2 is activated in thefirst mode and the second mode. However, the u-phase lower arm switchingelement Qu2 is activated in the first mode, and the w-phase lower armswitching element Qw2 is activated in the second mode. Thus, the firstmode and the second mode have different switching elements of the phasesthat are activated.

The control device 60 may be configured to variably control one of theswitching pattern and the duty ratio. For example, the control device 60may fix the switching pattern to one of the one-phase pattern and thetwo-phase pattern and variably control only on the duty ratio.Alternatively, the control device 60 may fix the duty ratio and switchthe switching pattern to the one-phase pattern or the two-phase pattern.The control device 60 only needs to variably control at least one of theswitching pattern and the duty ratio in accordance with the rotationalfrequency R.

The one-phase pattern may have any order of the lower arm switchingelement that is activated. For example, the one-phase pattern may beconfigured to switch the lower arm switching element that is activatedin order from the w-phase lower arm switching element Qw2 to the v-phaselower arm switching element Qv2 and then the u-phase lower arm switchingelement Qu2. The two-phase pattern may be configured in the same manner.

The two-phase pattern may have any combination of phases that aresimultaneously activated.

The switching pattern may have any specific mode as long as the subjectarm switching element that is activated is sequentially switched. Theswitching pattern may have a mode in which, for example, the subject armswitching elements are sequentially activated one phase at a time in apredetermined order between the three-phase activation periods, duringwhich the subject arm switching elements of the three phases are allactivated.

In the two-phase pattern of the embodiment, the lower arm switchingelements Qu2, Qv2, Qw2 rise to the activation state at differenttimings. Instead, the two-phase pattern may be, for example, a switchingpattern in which the lower arm switching elements of two phases rise tothe activation state at the same timing. For example, the two-phasepattern may be a pattern in which switching occurs in the order of Qu2,Qv2 are activated while Qw2 is deactivated; Qu2, Qv2, Qw2 aredeactivated; Qv2, Qw2 are activated while Qu2 is deactivated; Qu2, Qv2,Qw2 are deactivated; Qu2, Qw2 are activated while Qv2 is deactivated;Qu2, Qv2, Qw2 are deactivated; Qu2, Qv2 are activated while Qw2 isdeactivated; and so on. Thus, the two-phase pattern may be a switchingpattern in which the subject arm switching elements are sequentiallyactivated two phases at a time in a predetermined order between intervalperiods during which the subject arm switching elements of the threephases are all deactivated. In other words, the two-phase pattern onlyneeds to include at least one of a switching pattern including theinterval period, a switching pattern including the one-phase activationperiod, a switching pattern including the three-phase activation period,and a switching patter that does not include any of the interval period,the one-phase activation period, and the three-phase activation period.

In the embodiment, the lower arm switching elements Qu2, Qv2, Qw2 riseto the activation state at different timings. Thus, the switchingpattern is switched to the one-phase pattern or the two-phase pattern byadjusting the duty ratio. However, as described above, when the lowerarm switching elements Qu2, Qv2, Qw2 rise to the activation state at thesame timing (i.e., there is no phase difference), the adjustment of theduty ratio does not switch the switching pattern. Therefore, the dutyratio and the switching pattern may or may not be associated with eachother.

The control device 60 may have any specific structure for recognizingthe rotation direction and the rotational frequency R of the rotor 51.The structure may include, for example, a rotation angle sensor such asa resolver and perform the recognition based on the detection result ofthe rotation angle sensor.

When a predetermined condition is satisfied, for example, when therotational direction of the rotor 51 that is obtained by the recognitioncontrol is the reverse direction and the rotational frequency R that isobtained by the recognition process is less than or equal to apredetermined threshold value, the control device 60 does not have toexecute at least one of the deceleration control and the continuationcontrol. More specifically, the control device 60 is not limited to theconfiguration that always executes the deceleration control and thecontinuation control after the motor-driven compressor 10 is deactivated(i.e., when the rotor 51 reversely rotates). The control device 60 maybe configured to execute the deceleration control and the continuationcontrol when a specified condition is satisfied (e.g., when the reverserotational frequency R is greater than the above threshold value) afterthe motor-driven compressor 10 is deactivated. The control device 60only needs to function to perform the deceleration control and thecontinuation control.

The threshold value may be any value as long as the value is relativelysmall. The threshold value may be, for example, the target rotationalfrequency Rt or lower. Alternatively, the threshold value may be greaterthan the target rotational frequency Rt and less than the rotationalfrequency tolerance Ra. Alternatively, the threshold value may be, forexample, the rotational frequency tolerance Ra.

The injection ports 43 may be located at any position. Any number ofinjection ports 43 may be used.

The subject in which the motor-driven compressor 10 is installed is notlimited to a vehicle and may be any subject.

The motor-driven compressor 10 is used with the vehicle air conditioner100 but may be used with another device. For example, when the vehicleis a fuel cell vehicle (FCV) that includes a fuel cell, the motor-drivencompressor 10 may be used with a supply device that supplies air to thefuel cell. Thus, the compression subject may be any fluid. The fluid maybe a refrigerant or air.

The embodiment and modified examples may be combined. For example, thecontrol device 60 may be configured to switch the upper arm switchingelements Qu1, Qv1, Qw1 of the three phases to sequentially switch theupper arm switching element that is activated and then switch the lowerarm switching elements Qu2, Qv2, Qw2 of the three phases to sequentiallyswitch the lower arm switching element that is activated. Alternatively,the control device 60 is configured to switch the upper arm switchingelements Qu1, Qv1, Qw1 of the three phases or the lower arm switchingelements Qu2, Qv2, Qw2 of the three phases and then switch all of theswitching elements Qu1 to Qw2.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. A motor-driven compressor comprising: an electric motor including arotor; a housing including a suction port that draws in a fluid; acompression unit driven by the electric motor, wherein the compressionunit compresses an intake fluid, which is the fluid drawn in from thesuction port, and discharges a compressed fluid, which is the compressedintake fluid; a drive circuit that drives the electric motor; and acontroller that controls the drive circuit to control rotation of therotor, wherein the compression unit includes a fixed scroll fixed to thehousing, a movable scroll engaged with the fixed scroll and configuredto orbit the fixed scroll, and a compression chamber defined by thefixed scroll and the movable scroll, when the rotor rotates in apredetermined forward direction, the movable scroll orbits in theforward direction, and the compression unit thereby compresses theintake fluid drawn into the compression chamber, the motor-drivencompressor further comprises an injection port that draws anintermediate pressure fluid into the compression chamber, wherein theintermediate pressure fluid has a pressure that is higher than theintake fluid and lower than the compressed fluid, the controllerincludes a deceleration controller that performs a deceleration control,which decelerates the rotor, during a first period in response to therotor being rotating in a direction opposite to the forward direction,and a continuation controller that performs a continuation control,which continues the rotation of the rotor, during a second period thatis longer than the first period after the deceleration control isperformed, and a fluctuation difference of a rotational frequency of therotor during the continuation control is less than a decelerationrotational frequency difference, which is a difference between arotational frequency of the rotor when the deceleration control isstarted and a rotational frequency of the rotor when the decelerationcontrol is terminated.
 2. The motor-driven compressor according to claim1, wherein the deceleration controller is configured to decelerate therotor until the rotational frequency of the rotor becomes a targetrotational frequency, wherein the target rotational frequency is set tobe less than or equal to a predetermined rotational frequency tolerance,and the continuation controller is configured to continue the rotationof the rotor with the rotational frequency of the rotor maintained sothat the rotational frequency of the rotor is less than or equal to therotational frequency tolerance during the second period.
 3. Themotor-driven compressor according to claim 2, wherein the continuationcontroller is configured to control the drive circuit so that therotational frequency of the rotor is maintained at the target rotationalfrequency.
 4. The motor-driven compressor according to claim 1, whereinthe electric motor is a three-phase motor, the drive circuit includes au-phase upper arm switching element and a u-phase lower arm switchingelement connected to each other, a v-phase upper arm switching elementand a v-phase lower arm switching element connected to each other, and aw-phase upper arm switching element and a w-phase lower arm switchingelement connected to each other, the controller is configured to controlswitching of the upper arm switching elements of the three phases andthe lower arm switching elements of the three phases, and in thedeceleration control, the deceleration controller controls the drivecircuit in a switching control mode that includes a first mode, in whichone or more switching elements of the upper arm switching elements ofthe three phases and the lower arm switching elements of the threephases are activated while the remaining switching elements aredeactivated, and a second mode, which differs from the first mode in acombination of the activated and deactivated switching elements.
 5. Themotor-driven compressor according to claim 4, wherein the switchingcontrol mode in the deceleration control includes one of a mode thatswitches the upper arm switching elements of the three phases tosequentially switch the upper arm switching element that is activated, amode that switches the lower arm switching elements of the three phasesto sequentially switch the lower arm switching element that isactivated, and a mode that switches the upper arm switching elements ofthe three phases and the lower arm switching elements of the threephases to sequentially switch the switching element that is activatedwithout simultaneously activating the upper arm switching element andthe lower arm switching element of the same phase.
 6. The motor-drivencompressor according to claim 5, wherein the deceleration controller isconfigured to start the deceleration control by cyclically activatingand deactivating subject arm switching elements of the three phases,which are subject to switching, using a predetermined initialdeceleration switching pattern and a predetermined initial decelerationduty ratio and then variably control at least one of a switching patternand a duty ratio of the subject arm switching elements of the threephases so that a current flowing to the three-phase motor increases in arange that does not exceed a predetermined tolerance value.
 7. Themotor-driven compressor according to claim 6, wherein the initialdeceleration switching pattern and the initial deceleration duty ratioare set so that the current flowing to the three-phase motor does notexceed the tolerance value regardless of the rotational frequency of therotor.
 8. The motor-driven compressor according to claim 4, wherein thecontinuation controller is configured to start the continuation controlby cyclically activating and deactivating the subject arm switchingelements of the three phases, which are either or both of the upper armswitching elements of the three phases and the lower arm switchingelements of the three phases, using a predetermined initial continuationswitching pattern and a predetermined initial continuation duty ratioand then variably control at least one of a switching pattern and a dutyratio of the subject arm switching elements of the three phases togradually decrease a current flowing to the three-phase motor.
 9. Themotor-driven compressor according to claim 1, wherein the controller isconfigured to perform a deactivation control that stops the rotation ofthe rotor after terminating the continuation control.